The present invention relates generally to electric machines and, in particular, to a core slot insulator for an electric machine having a core and a winding. Electric machines, such as alternating current electric generators, or alternators are well known. Prior art alternators typically include a stator assembly and a rotor assembly disposed in a alternator housing. The stator assembly is mounted to the housing and includes a generally cylindrically-shaped stator core having a plurality of slots formed therein. The rotor assembly includes a motor rotor attached to a generally cylindrical shaft that is rotatably mounted in the housing and is coaxial with the stator assembly. The stator assembly includes a plurality of wires wound thereon, forming windings. The stator windings are formed of slot segments that are located in the core slots and end loop segments that connect two adjacent slot segments of each phase and are formed in a predetermined multi-phase (e.g. three or six) winding pattern in the slots of the stator core. The slot segments are typically insulated from the core by a sheet type insulator or a coating. The term sheet type insulator, utilized herein, is used to describe an insulator that is formed from a flat member, which is folded to form the U-shaped insulator. A typical sheet type insulator well known to those skilled in the art is a film/nomex laminate and they are commonly known as “slot liners” to those skilled in the art. The rotor assembly can be any type of rotor assembly, such as a “claw-pole” rotor assembly, which typically includes opposed poles as part of claw fingers that are positioned around an electrically charged rotor coil. The rotor coil produces a magnetic field in the claw fingers. As a prime mover, such as a steam turbine, a gas turbine, or a drive belt from an automotive internal combustion engine, rotates the rotor assembly, the magnetic field of the rotor assembly passes through the stator windings, inducing an alternating electrical current in the stator windings in a well known manner. The alternating electrical current is then routed from the alternator to a distribution system for consumption by electrical devices or, in the case of an automotive alternator, to a rectifier and then to a charging system for an automobile battery.
One type of device is a high slot fill stator, which is characterized by rectangular shaped conductors whose width, including any insulation fit, closely to the width, including any insulation of the rectangular shaped core slots. High slot fill stators are advantageous because they are efficient and help produce more electrical power per winding than other types of prior art stators. A disadvantage of the high slot fill stators is the difficulty of inserting the wires whose width fits closely to the width of the slots. The potential of the windings to catch the edge of the slot liner as the windings are inserted, thereby damaging the slot liner and causing an electrical ground from the winding to the core is rather large. To compound this problem, the slot liners of a high slot fill stator are typically very thin in thickness to allow for a greater slot fill numbers. A thin material has less column strength and therefore is more likely to intrude into the slot and be caught by the conductors as they are inserted. One commonly known method employed to counteract this potential failure is to create the winding from U shaped conductors that are axially inserted into the core slots. This may solve the slot liner issue but it disadvantageously creates a difficult process of welding the U shaped segments together to form the winding. Another method employed to solve the slot liner issue is to insert the windings into a flat lamination stack and roll the lamination stack and winding assembly into the desired cylindrically-shaped shape. The flat stack inherently has a wider slot opening, which eases the step of successfully inserting conductors into the slots beyond the slot liners, but it also disadvantageously introduces a process of rolling the core/winding assembly and welding the core ends.
It is desirable, therefore, to provide a stator assembly that meets the requirements of a high slot fill stator including conductors having slot segments with a width, including any insulation, that closely fits to the width, including any insulation, of the core slot, and being radially inserted into a cylindrically-shaped core which does not potentially damage the slot liners.